1. Field of the Invention
The present invention relates to a substrate to be processed (precursor substrate for processing) having a metal film or a metal compound film to be microfabricated by an electron beam lithography and having laminated thereon a resist film for electron beam and an organic conductive film and, a method for producing the substrate to be processed, and a resist patterning process by using the substrate to be processed; in particular, the present invention relates to a photomask blank having laminated thereon a resist film for electron beam and an organic conductive film used for producing a photomask used in microfabrication of a semiconductor integrated circuit, CCD (Charge Coupled Device), a color filter for LCD (Liquid Crystal Display), a magnetic head, and the like.
2. Description of the Related Art
In recent years, especially with progress of a large-scale integrated circuit toward higher integration in semiconductor processing, requirement of miniaturization in a circuit pattern is increasing more than ever, so that requirement of a further finer line of a wiring pattern to constitute a circuit and requirement of a miniaturization technology in a contact hole pattern for wiring among layers that constitute a cell are increasing more and more. Accordingly, with the progress of miniaturization, a technology to draw a circuit pattern more finely and accurately is also sought in production of a photomask drawn with a circuit pattern used in a photolithography to form the wiring pattern and the contact hole pattern as mentioned above.
Meanwhile, in general, the forgoing photomask processing is carried out by a method wherein a resist film is formed on a photomask blank having an optical film such as a light-shielding film and a phase shift film formed on a transparent substrate absorbing almost no exposing light or, on the contrary, on a substrate reflecting an exposing light, then an electron beam is irradiated onto the resist film thus formed to make a resist pattern, which is then transferred to the light-shielding film or the phase shift film by etching.
In this processing, formation of the resist pattern by irradiation of an electron beam must be conducted with an extremely accurate positioning; but because a resist film usually used is an insulator, an electric accumulation (charge-up) occurs in the resist film sometimes. Because of this charge-up effect, the electron beam irradiated onto a photomask blank surface is distorted thereby causing a slight misalignment in the resist pattern position formed, namely causing a decrease in the resist pattern accuracy.
To prevent the charge-up from occurring during patterning by irradiation of an electron beam on a resist film, it is known that a method, wherein an electron beam is irradiated to a conductive polymer layer formed on a resist film, is effective—and for example, a method also usable on a chemical amplification resist is disclosed in Japanese Patent Laid-Open (Kokai) No. H08-109351 and Japanese Patent Laid-Open (Kokai) No. 2006-117925.